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| Many single tenant users of high performance optical fiber are implementing data networks with centralized electronics versus distributed electronics in the building. Centralized optical fiber cabling is designed as an alternative to the optical cross-connection located in the telecommunications room when deploying recognized optical fiber cable in the horizontal in support of centralized electronics. Centralized cabling provides connections from work areas to centralized cross-connects by the use of pull-through cables, an interconnection, or splice. The horizontal cross-connection as specified in ANSI/TIA/EIA-568-B.1 and ANSI/TIA/EIA-568-B.3 provides the user with maximum flexibility, specifically in the deployment of distributed electronics or in multi-tenant buildings. Careful planning and implementation of centralized optical fiber cabling will help assure that the user maintains adequate flexibility and manageability with the cabling network. Applicability The guidelines and requirements for centralized optical fiber cabling networks are intended for those single-tenant users who desire to deploy centralized electronics rather than distributed electronics and want an alternative to locating the cross-connection in the telecommunications room. General guidelines This specifies the use of either pull-through cables, an interconnection, or splice in the telecommunications room. The use of an interconnection between the backbone and horizontal cabling is recognized to offer increased flexibility, manageability, and ease to migrate to a cross-connection. Requirements The specifications of ANSI/TIA/EIA-569-A shall be followed. The maximum horizontal cabling distance is as specified in clause 4. The installation shall be limited to 300 m (984 ft) consisting of the combined length of the horizontal, intrabuilding backbone, and patch cords. Adhering to the 300 m (984 ft) limitation will ensure that the recognized cabling system will support multi-gigabit services using centralized electronics. Centralized cabling implementations shall be located within the same building as the work areas served. The administration of moves and changes shall be performed at the centralized cross-connect. The pull-through cable length shall be less than or equal to 90 m (295 ft). Pull-through cables shall meet the same requirements of recognized horizontal optical fiber cable per clause 4 of ANSI/TIA/EIA-568-B.3. Centralized cabling design shall allow for migration (in part or in total) of the pull-through, interconnect, or splice implementation to a cross-connection implementation. Sufficient space shall be left in the telecommunications room to allow for the addition of patch panels needed for the migration of the pull-through, interconnect, or splice to a cross-connection. Sufficient cable slack shall exist in the telecommunications room to allow movement of the cables when migrating to a cross-connection. NOTE 1 - Pull-through cables are continuous sheath cables that are pulled through a telecommunications room from the centralized cross-connect to the telecommunications outlet/connector. Slack storage shall provide bend radius control so that cable and fiber bend radius limitations are not violated. Fiber slack shall be stored in protective enclosures. Centralized cabling design shall allow for the addition and removal of horizontal and intrabuilding backbone fibers. Recommendations The addition and removal of horizontal links should be performed at the telecommunications room. Slack may be stored as cable or unjacketed fiber (buffered or coated). Cable slack may be stored within enclosures or on the walls of the telecommunications room. The layout of both rack-mount and wall-mount termination hardware should accommodate modular growth in an orderly manner. NOTE - Specifications on pull-through implementations apply equally to all media types. Cross-connects for different media types are required to be in the same location.
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